Every time you visit a website, all the resources will be downloaded to your browser.

The download may require multiple round-trip journeys between the browser and the server, which slows down processing and can block rendering of page content, as well as causing data costs for the visitor.

All server responses need to specify a cache policy to help the browser determine in which situations it is possible to reuse a previously searched response.

On Apache servers, it is possible to determine cache validators via .htaccess of each site file type.